The spleen is a fist-sized organ situated in the upper left side of the abdomen, beneath the rib cage. As a highly vascular component of the lymphatic system, it filters blood, removes old and damaged blood cells, and contributes to immune defenses. While cancer that starts directly within the spleen is extremely rare, the organ is frequently involved in malignancies originating elsewhere. This secondary involvement is common, particularly with cancers affecting the blood and lymphatic system, such as leukemias and lymphomas.
Understanding Primary Spleen Cancer
Cancer can originate in the spleen, but this is an uncommon occurrence compared to involvement in other organs. When a malignancy starts directly within the spleen tissue, it is classified as a primary spleen cancer. These primary splenic cancers account for a very small fraction of all cancers diagnosed.
The most frequent type of primary malignancy is Primary Splenic Lymphoma, a cancer of the lymphatic tissue within the organ. This is considered a subtype of non-Hodgkin lymphoma. Another form is Splenic Angiosarcoma, a highly aggressive tumor that develops from the cells lining the blood vessels.
Splenic Angiosarcoma is particularly rare, with an estimated prevalence of less than one case per million people. Since the spleen is composed mainly of lymphoid and vascular tissue, primary tumors tend to be of these types. Diagnosing a primary splenic malignancy requires confirming that the cancer has not spread from another site.
Spleen Involvement in Systemic Cancers
The spleen is far more often affected by cancers that start in other parts of the body, a situation referred to as secondary involvement. Its structure as a large filter for the bloodstream and a major component of the immune system makes it susceptible to diseases affecting the lymphatic and circulatory systems.
Cancers of the blood and lymph, such as lymphomas and leukemias, frequently manifest in the spleen. This occurs because the spleen is rich in the same immune cells where these malignancies begin. Lymphomas often spread to the spleen through the connected lymphatic network, and leukemia cells can infiltrate and accumulate there.
The infiltration of cancer cells often causes the spleen to become enlarged, a condition known as splenomegaly. This enlargement occurs as the spleen attempts to filter abnormal cells or as malignant cells multiply within the organ. Splenomegaly is a common physical sign pointing toward splenic involvement in systemic cancers.
Solid tumors can also spread to the spleen through metastasis. Cancers originating in sites like the lung, breast, or stomach can travel through the bloodstream, forming metastatic lesions. However, the spleen’s unique immune environment makes it a less common site for solid tumor metastasis compared to organs like the liver or lungs.
Recognizing Symptoms and Diagnosis
Symptoms associated with splenic malignancies or enlargement can be subtle and non-specific. The most common symptom is pain or a feeling of fullness in the upper left side of the abdomen, caused by the physical pressure of an enlarged spleen. This discomfort may occur after eating, due to the enlarged organ pressing on the stomach.
Systemic symptoms, often referred to as B symptoms, are common with lymphomas and leukemias involving the spleen. These include unexplained weight loss, drenching night sweats, and persistent fever. Fatigue and weakness may also be present due to associated anemia.
The diagnostic process begins with a physical examination, where a doctor may feel an enlarged spleen beneath the rib cage. Blood tests, such as a complete blood count, look for abnormalities in blood cell levels, like low counts of red cells or platelets (cytopenias). These changes can signal that the spleen is over-filtering the blood or that the bone marrow is affected by a blood cancer.
Imaging studies are routinely used to visualize the spleen and surrounding structures. An ultrasound can confirm enlargement, while Computed Tomography (CT) scans and Positron Emission Tomography (PET) scans provide detailed images to identify masses or widespread disease. Ultimately, confirming the exact type of cancer, whether primary or secondary, usually requires a biopsy. This involves collecting a small tissue sample from the spleen or another affected site for microscopic analysis.
Treatment Strategies and Prognosis
Treatment for a splenic malignancy depends on whether the cancer started in the spleen or spread there, as well as the specific type and stage of the disease. For primary splenic cancers, such as localized lymphomas, surgery to remove the spleen (splenectomy) may be a curative option. Splenectomy is also performed to alleviate severe symptoms, such as significant pain or dangerously low blood cell counts caused by a massively enlarged spleen.
Systemic treatments are the main approach for most secondary splenic involvement, such as in leukemia or widespread lymphoma, targeting cancer cells throughout the body.
Systemic Treatment Options
- Chemotherapy uses strong drugs to kill rapidly dividing cells.
- Targeted therapy focuses on specific molecular features of the cancer cells for a more precise attack.
- Immunotherapy harnesses the body’s own immune system to fight cancer, and is an important modality, especially for certain types of lymphoma.
The outlook for a person with a splenic malignancy varies widely based on the underlying diagnosis. For some indolent types of splenic lymphoma, the prognosis can be favorable, with long periods of disease control achieved through treatment. In contrast, primary splenic angiosarcoma has a significantly poorer prognosis due to its aggressive nature and tendency to be diagnosed at an advanced stage. Overall survival depends on the responsiveness of the specific cancer type to systemic therapies and the extent of the disease.